Such a damper is described in EP-A-0 475 283 and its corresponding U.S. Pat. No. 5,209,334, which discloses (FIGS. 8 and 9) a damper having second elastic members fitted radially under first elastic members, and elastically gripping friction means which comprise at least a first axially acting elastic washer, which axially urges the reaction plates towards the wheel disc to induce friction between said plates and the wheel disc, so that the reaction plates are separate from one another.
Thus the wheel disc has good mechanical strength, the second elastic members are spared when the first elastic members intervene, and the reaction plates have a double role, i.e. a role as guide washers for the second elastic members, and a friction role with the wheel disc. They follow the movement of the wheel disc during the deferred intervention of the first elastic members.
In this arrangement it is however difficult to control the friction between the parts.
In fact the reaction plates are made partly of metal and partly from plastic material. By their metal part they are shaped frictionally to engage respectively one of the guide washers and the first elastic washer after the action of the first elastic members; by their part made from plastic, they are adapted frictionally to engage the wheel disc during the action of the second elastic members.